Works great, but will block the second USB-C port on your MacBook Pro
I use this now that I have a MacBook Pro with USB-C ports and no card slot. Works just fine. It might be a little slower than having a built in card slot, but if it is, the difference isn't noticeable.
It's wide enough to block the second USB-C port on your MacBook Pro. Also, it feels a bit vulnerable having the relatively large surface area hanging off of a small port, so a little caution is required.